1. Field of the Invention
The present invention relates generally to power transmission in tracked vehicles such as tanks and more specifically to an improved drive assembly for powering a steering unit and a vehicle propulsion gear box.
2. Brief Description of the Prior Art
Drive assemblies for tracked vehicles having a hydrodynamic-mechanical speed change gear box for vehicle propulsion, i.e. travelling drive, and with an infinitely variable superimposed steering unit have been disclosed in the following patents: Federal Republic of Germany Pat. No. 1,480,725 (corresponding to United Kingdom Pat. No. 1,155,867) and Federal Republic of Germany application No. 2,521,331 (corresponding to United Kingdom Pat. No. 1,526,542). The vehicle engines which drove such assemblies were either diesel or multiple shaft gas turbines with the working turbine wheel shaft separate from the gas compressor stage.
The infinitely variable steering unit was preferably driven from the primary side of a hydrodyanmic converter while the speed change gear box (for vehicle propulsion) was driven from the secondary side of the converter. The slip provided by the hydrodynamic converter permitted the steering unit to achieve practically full driving speed in the starting state, with the secondary side of the converter rotating slowly or not rotating at all.
The employment of hydrodynamic converters for power distribution between the speed change gear box and the steering unit presented certain disadvantages. Initially, the hydrodynamic converter increased the size, weight and cost of the drive assembly. In addition, the converter provided a component in the drive assembly which was a potential source of malfunction.